acpi_pad.c

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/*
 * acpi_pad.c ACPI Processor Aggregator Driver
 *
 * Copyright (c) 2009, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

#include <linux/kernel.h>
#include <linux/cpumask.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/cpu.h>
#include <linux/clockchips.h>
#include <linux/slab.h>
#include <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>
#include <asm/mwait.h>

#define ACPI_PROCESSOR_AGGREGATOR_CLASS "acpi_pad"
#define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"
#define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80
static DEFINE_MUTEX(isolated_cpus_lock);
static DEFINE_MUTEX(round_robin_lock);

static unsigned long power_saving_mwait_eax;

static unsigned char tsc_detected_unstable;
static unsigned char tsc_marked_unstable;
static unsigned char lapic_detected_unstable;
static unsigned char lapic_marked_unstable;

static void power_saving_mwait_init(void)
{
    unsigned int eax, ebx, ecx, edx;
    unsigned int highest_cstate = 0;
    unsigned int highest_subcstate = 0;
    int i;

    if (!boot_cpu_has(X86_FEATURE_MWAIT))
        return;
    if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
        return;

    cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);

    if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
        !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
        return;

    edx >>= MWAIT_SUBSTATE_SIZE;
    for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
        if (edx & MWAIT_SUBSTATE_MASK) {
            highest_cstate = i;
            highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
        }
    }
    power_saving_mwait_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
        (highest_subcstate - 1);

#if defined(CONFIG_X86)
    switch (boot_cpu_data.x86_vendor) {
    case X86_VENDOR_AMD:
    case X86_VENDOR_INTEL:
        /*
         * AMD Fam10h TSC will tick in all
         * C/P/S0/S1 states when this bit is set.
         */
        if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
            tsc_detected_unstable = 1;
        if (!boot_cpu_has(X86_FEATURE_ARAT))
            lapic_detected_unstable = 1;
        break;
    default:
        /* TSC & LAPIC could halt in idle */
        tsc_detected_unstable = 1;
        lapic_detected_unstable = 1;
    }
#endif
}

static unsigned long cpu_weight[NR_CPUS];
static int tsk_in_cpu[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
static DECLARE_BITMAP(pad_busy_cpus_bits, NR_CPUS);
static void round_robin_cpu(unsigned int tsk_index)
{
    struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
    cpumask_var_t tmp;
    int cpu;
    unsigned long min_weight = -1;
    unsigned long uninitialized_var(preferred_cpu);

    if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
        return;

    mutex_lock(&round_robin_lock);
    cpumask_clear(tmp);
    for_each_cpu(cpu, pad_busy_cpus)
        cpumask_or(tmp, tmp, topology_thread_cpumask(cpu));
    cpumask_andnot(tmp, cpu_online_mask, tmp);
    /* avoid HT sibilings if possible */
    if (cpumask_empty(tmp))
        cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);
    if (cpumask_empty(tmp)) {
        mutex_unlock(&round_robin_lock);
        return;
    }
    for_each_cpu(cpu, tmp) {
        if (cpu_weight[cpu] < min_weight) {
            min_weight = cpu_weight[cpu];
            preferred_cpu = cpu;
        }
    }

    if (tsk_in_cpu[tsk_index] != -1)
        cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
    tsk_in_cpu[tsk_index] = preferred_cpu;
    cpumask_set_cpu(preferred_cpu, pad_busy_cpus);
    cpu_weight[preferred_cpu]++;
    mutex_unlock(&round_robin_lock);

    set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));
}

static void exit_round_robin(unsigned int tsk_index)
{
    struct cpumask *pad_busy_cpus = to_cpumask(pad_busy_cpus_bits);
    cpumask_clear_cpu(tsk_in_cpu[tsk_index], pad_busy_cpus);
    tsk_in_cpu[tsk_index] = -1;
}

static unsigned int idle_pct = 5; /* percentage */
static unsigned int round_robin_time = 1; /* second */
static int power_saving_thread(void *data)
{
    struct sched_param param = {.sched_priority = 1};
    int do_sleep;
    unsigned int tsk_index = (unsigned long)data;
    u64 last_jiffies = 0;

    sched_setscheduler(current, SCHED_RR, &param);

    while (!kthread_should_stop()) {
        int cpu;
        u64 expire_time;

        try_to_freeze();

        /* round robin to cpus */
        if (last_jiffies + round_robin_time * HZ < jiffies) {
            last_jiffies = jiffies;
            round_robin_cpu(tsk_index);
        }

        do_sleep = 0;

        expire_time = jiffies + HZ * (100 - idle_pct) / 100;

        while (!need_resched()) {
            if (tsc_detected_unstable && !tsc_marked_unstable) {
                /* TSC could halt in idle, so notify users */
                mark_tsc_unstable("TSC halts in idle");
                tsc_marked_unstable = 1;
            }
            if (lapic_detected_unstable && !lapic_marked_unstable) {
                int i;
                /* LAPIC could halt in idle, so notify users */
                for_each_online_cpu(i)
                    clockevents_notify(
                        CLOCK_EVT_NOTIFY_BROADCAST_ON,
                        &i);
                lapic_marked_unstable = 1;
            }
            local_irq_disable();
            cpu = smp_processor_id();
            if (lapic_marked_unstable)
                clockevents_notify(
                    CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
            stop_critical_timings();

            __monitor((void *)&current_thread_info()->flags, 0, 0);
            smp_mb();
            if (!need_resched())
                __mwait(power_saving_mwait_eax, 1);

            start_critical_timings();
            if (lapic_marked_unstable)
                clockevents_notify(
                    CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
            local_irq_enable();

            if (jiffies > expire_time) {
                do_sleep = 1;
                break;
            }
        }

        /*
         * current sched_rt has threshold for rt task running time.
         * When a rt task uses 95% CPU time, the rt thread will be
         * scheduled out for 5% CPU time to not starve other tasks. But
         * the mechanism only works when all CPUs have RT task running,
         * as if one CPU hasn't RT task, RT task from other CPUs will
         * borrow CPU time from this CPU and cause RT task use > 95%
         * CPU time. To make 'avoid starvation' work, takes a nap here.
         */
        if (do_sleep)
            schedule_timeout_killable(HZ * idle_pct / 100);
    }

    exit_round_robin(tsk_index);
    return 0;
}

static struct task_struct *ps_tsks[NR_CPUS];
static unsigned int ps_tsk_num;
static int create_power_saving_task(void)
{
    int rc = -ENOMEM;

    ps_tsks[ps_tsk_num] = kthread_run(power_saving_thread,
        (void *)(unsigned long)ps_tsk_num,
        "acpi_pad/%d", ps_tsk_num);
    rc = IS_ERR(ps_tsks[ps_tsk_num]) ? PTR_ERR(ps_tsks[ps_tsk_num]) : 0;
    if (!rc)
        ps_tsk_num++;
    else
        ps_tsks[ps_tsk_num] = NULL;

    return rc;
}

static void destroy_power_saving_task(void)
{
    if (ps_tsk_num > 0) {
        ps_tsk_num--;
        kthread_stop(ps_tsks[ps_tsk_num]);
        ps_tsks[ps_tsk_num] = NULL;
    }
}

static void set_power_saving_task_num(unsigned int num)
{
    if (num > ps_tsk_num) {
        while (ps_tsk_num < num) {
            if (create_power_saving_task())
                return;
        }
    } else if (num < ps_tsk_num) {
        while (ps_tsk_num > num)
            destroy_power_saving_task();
    }
}

static void acpi_pad_idle_cpus(unsigned int num_cpus)
{
    get_online_cpus();

    num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
    set_power_saving_task_num(num_cpus);

    put_online_cpus();
}

static uint32_t acpi_pad_idle_cpus_num(void)
{
    return ps_tsk_num;
}

static ssize_t acpi_pad_rrtime_store(struct device *dev,
    struct device_attribute *attr, const char *buf, size_t count)
{
    unsigned long num;
    if (strict_strtoul(buf, 0, &num))
        return -EINVAL;
    if (num < 1 || num >= 100)
        return -EINVAL;
    mutex_lock(&isolated_cpus_lock);
    round_robin_time = num;
    mutex_unlock(&isolated_cpus_lock);
    return count;
}

static ssize_t acpi_pad_rrtime_show(struct device *dev,
    struct device_attribute *attr, char *buf)
{
    return scnprintf(buf, PAGE_SIZE, "%d\n", round_robin_time);
}
static DEVICE_ATTR(rrtime, S_IRUGO|S_IWUSR,
    acpi_pad_rrtime_show,
    acpi_pad_rrtime_store);

static ssize_t acpi_pad_idlepct_store(struct device *dev,
    struct device_attribute *attr, const char *buf, size_t count)
{
    unsigned long num;
    if (strict_strtoul(buf, 0, &num))
        return -EINVAL;
    if (num < 1 || num >= 100)
        return -EINVAL;
    mutex_lock(&isolated_cpus_lock);
    idle_pct = num;
    mutex_unlock(&isolated_cpus_lock);
    return count;
}

static ssize_t acpi_pad_idlepct_show(struct device *dev,
    struct device_attribute *attr, char *buf)
{
    return scnprintf(buf, PAGE_SIZE, "%d\n", idle_pct);
}
static DEVICE_ATTR(idlepct, S_IRUGO|S_IWUSR,
    acpi_pad_idlepct_show,
    acpi_pad_idlepct_store);

static ssize_t acpi_pad_idlecpus_store(struct device *dev,
    struct device_attribute *attr, const char *buf, size_t count)
{
    unsigned long num;
    if (strict_strtoul(buf, 0, &num))
        return -EINVAL;
    mutex_lock(&isolated_cpus_lock);
    acpi_pad_idle_cpus(num);
    mutex_unlock(&isolated_cpus_lock);
    return count;
}

static ssize_t acpi_pad_idlecpus_show(struct device *dev,
    struct device_attribute *attr, char *buf)
{
    int n = 0;
    n = cpumask_scnprintf(buf, PAGE_SIZE-2, to_cpumask(pad_busy_cpus_bits));
    buf[n++] = '\n';
    buf[n] = '\0';
    return n;
}
static DEVICE_ATTR(idlecpus, S_IRUGO|S_IWUSR,
    acpi_pad_idlecpus_show,
    acpi_pad_idlecpus_store);

static int acpi_pad_add_sysfs(struct acpi_device *device)
{
    int result;

    result = device_create_file(&device->dev, &dev_attr_idlecpus);
    if (result)
        return -ENODEV;
    result = device_create_file(&device->dev, &dev_attr_idlepct);
    if (result) {
        device_remove_file(&device->dev, &dev_attr_idlecpus);
        return -ENODEV;
    }
    result = device_create_file(&device->dev, &dev_attr_rrtime);
    if (result) {
        device_remove_file(&device->dev, &dev_attr_idlecpus);
        device_remove_file(&device->dev, &dev_attr_idlepct);
        return -ENODEV;
    }
    return 0;
}

static void acpi_pad_remove_sysfs(struct acpi_device *device)
{
    device_remove_file(&device->dev, &dev_attr_idlecpus);
    device_remove_file(&device->dev, &dev_attr_idlepct);
    device_remove_file(&device->dev, &dev_attr_rrtime);
}

/*
 * Query firmware how many CPUs should be idle
 * return -1 on failure
 */
static int acpi_pad_pur(acpi_handle handle)
{
    struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
    union acpi_object *package;
    int num = -1;

    if (ACPI_FAILURE(acpi_evaluate_object(handle, "_PUR", NULL, &buffer)))
        return num;

    if (!buffer.length || !buffer.pointer)
        return num;

    package = buffer.pointer;

    if (package->type == ACPI_TYPE_PACKAGE &&
        package->package.count == 2 &&
        package->package.elements[0].integer.value == 1) /* rev 1 */

        num = package->package.elements[1].integer.value;

    kfree(buffer.pointer);
    return num;
}

/* Notify firmware how many CPUs are idle */
static void acpi_pad_ost(acpi_handle handle, int stat,
    uint32_t idle_cpus)
{
    union acpi_object params[3] = {
        {.type = ACPI_TYPE_INTEGER,},
        {.type = ACPI_TYPE_INTEGER,},
        {.type = ACPI_TYPE_BUFFER,},
    };
    struct acpi_object_list arg_list = {3, params};

    params[0].integer.value = ACPI_PROCESSOR_AGGREGATOR_NOTIFY;
    params[1].integer.value =  stat;
    params[2].buffer.length = 4;
    params[2].buffer.pointer = (void *)&idle_cpus;
    acpi_evaluate_object(handle, "_OST", &arg_list, NULL);
}

static void acpi_pad_handle_notify(acpi_handle handle)
{
    int num_cpus;
    uint32_t idle_cpus;

    mutex_lock(&isolated_cpus_lock);
    num_cpus = acpi_pad_pur(handle);
    if (num_cpus < 0) {
        mutex_unlock(&isolated_cpus_lock);
        return;
    }
    acpi_pad_idle_cpus(num_cpus);
    idle_cpus = acpi_pad_idle_cpus_num();
    acpi_pad_ost(handle, 0, idle_cpus);
    mutex_unlock(&isolated_cpus_lock);
}

static void acpi_pad_notify(acpi_handle handle, u32 event,
    void *data)
{
    struct acpi_device *device = data;

    switch (event) {
    case ACPI_PROCESSOR_AGGREGATOR_NOTIFY:
        acpi_pad_handle_notify(handle);
        acpi_bus_generate_proc_event(device, event, 0);
        acpi_bus_generate_netlink_event(device->pnp.device_class,
            dev_name(&device->dev), event, 0);
        break;
    default:
        printk(KERN_WARNING "Unsupported event [0x%x]\n", event);
        break;
    }
}

static int acpi_pad_add(struct acpi_device *device)
{
    acpi_status status;

    strcpy(acpi_device_name(device), ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME);
    strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);

    if (acpi_pad_add_sysfs(device))
        return -ENODEV;

    status = acpi_install_notify_handler(device->handle,
        ACPI_DEVICE_NOTIFY, acpi_pad_notify, device);
    if (ACPI_FAILURE(status)) {
        acpi_pad_remove_sysfs(device);
        return -ENODEV;
    }

    return 0;
}

static int acpi_pad_remove(struct acpi_device *device,
    int type)
{
    mutex_lock(&isolated_cpus_lock);
    acpi_pad_idle_cpus(0);
    mutex_unlock(&isolated_cpus_lock);

    acpi_remove_notify_handler(device->handle,
        ACPI_DEVICE_NOTIFY, acpi_pad_notify);
    acpi_pad_remove_sysfs(device);
    return 0;
}

static const struct acpi_device_id pad_device_ids[] = {
    {"ACPI000C", 0},
    {"", 0},
};
MODULE_DEVICE_TABLE(acpi, pad_device_ids);

static struct acpi_driver acpi_pad_driver = {
    .name = "processor_aggregator",
    .class = ACPI_PROCESSOR_AGGREGATOR_CLASS,
    .ids = pad_device_ids,
    .ops = {
        .add = acpi_pad_add,
        .remove = acpi_pad_remove,
    },
};

static int __init acpi_pad_init(void)
{
    power_saving_mwait_init();
    if (power_saving_mwait_eax == 0)
        return -EINVAL;

    return acpi_bus_register_driver(&acpi_pad_driver);
}

static void __exit acpi_pad_exit(void)
{
    acpi_bus_unregister_driver(&acpi_pad_driver);
}

module_init(acpi_pad_init);
module_exit(acpi_pad_exit);
MODULE_AUTHOR("Shaohua Li<[email protected]>");
MODULE_DESCRIPTION("ACPI Processor Aggregator Driver");
MODULE_LICENSE("GPL");